This invention relates to a door closer and particularly relates to a door closer with a back check adjustment and further relates to a door closer with facility for extracting a gaseous medium from a fluid used in the operation of the door closer.
Door closers typically are formed by a cylinder which is coupled to a spring tube to form an enclosed main chamber containing fluid (e.g. oil) within the cylinder and tube. A piston is located within the cylinder for movement within the chamber. At least one coil spring is located within the tube portion of the chamber and is in axial engagement with one end of the piston to normally urge the piston into the cylinder portion of the chamber when the associated door is closed.
An elongated opening is formed through the piston and extends from near one end of the piston to near the other end thereof. One side wall of the elongated opening is formed with teeth to form a rack. A pinion is located within the elongated opening so that the teeth of the pinion mesh with the teeth of the rack.
Driving elements are formed on opposite sides of the pinion and extend through the sidewall of the cylinder to allow coupling of the driving elements and the pinion to facilities external of the cylinder.
A door closer of this type can be mounted on one surface of a door near the top where one of the driving elements is coupled to one end of a first linkage arm. The other end of the first arm is coupled to one end of a second linkage arm for hinged movement relative thereto while the other end of the second arm is coupled for pivotal movement to a bracket which is fixedly secured to the door frame.
When the door is in the closed position, the linkage arms are positioned so that the spring is urging the piston into the end of the cylinder portion of the chamber which is furthest from the spring tube. As the door is opened, the linkage arms are moved so that the first arm causes the driving element and pinion to rotate about the axis of the pinion. As the pinion rotates, the mesh of the pinion and rack teeth cause the piston to move against the biasing action of the spring and toward the tube portion of the chamber.
A reserve chamber or reservoir is formed in the cylinder and communicates with the main chamber through a main passageway and a back-check passageway of restricted opening formed in the cylinder wall. As the piston is moved upon opening of the door, some of the fluid is initially urged from the main chamber through the main passageway and the back-check passageway of restricted opening and into the reservoir. Eventually, the piston is moved sufficiently to cover the main passageway whereby the fluid now travels only through the back-check passageway into the reservoir. This condition occurs, for example, when the door is opened about sixty to seventy-five degrees from a closed position. The fluid now begins to be compressed within the main chamber with the only outlet being through the back-check passageway and thereby provides a "back check" condition to prevent the door from being swung open too swiftly.
A back-check valve is located in the back-check passageway and allows for adjustment of the restricted opening of the passageway to control the volume of fluid allowed to pass to the reservoir during a given period. Thus, for doors that are opened in a normal manner, the "back check" adjustment permits the user to establish the degree to which the movement of the door will create a counterforce in opposition to further movement of the door beyond the position of the sixty to seventy- five degrees opening. This protects the door, the surrounding door support structure, the person opening the door and anyone in the path of the door being opened. However, if the door is opened in a violet or swift manner, the fluid still can only pass through the back check valve at a rate determined by the manually adjusted setting. In this situation, the fluid cannot pass quickly enough into the reservoir and is suddenly compressed within the main chamber to develop a significant back pressure. In response to the continued violent force of opening the door, the door could be violently separated from the frame causing serious damage to the door and support structure and serious injury to anyone in the area of the door including the person opening the door.
The typical back-check valve includes a threaded plunger with a slightly tapered tip which can be adjustably positioned adjacent a port associated with the back-check passageway. In this manner, as the plunger is adjusted inwardly, more of the port is covered to effectively control the rate of the fluid allowed to pass therethrough.
As long as the door closer operates in a consistent temperature environment, the back-check valve can be adjusted to a desired position and the position of the door at which the "back check" condition will occur at all times is generally at the same degrees opening and resistance. However, most doors are located in an environment which has considerable temperature swings as the seasons of the year pass as well as for other reasons. Under these changing-temperature conditions, the viscosity of the fluid changes to the extent that the "back check" condition will change so that the resistance will be at an undesirable level.
Thus, there is a need for a back-check valve which will respond to the force of opening the door, whether such opening be in a normal fashion with a moderate force or in a violent manner with an exceptional force, and allow for the development of sufficient counterforce in the establishment of the "back-check" condition. Further, there is a need for a back-check valve which will allow for the development of sufficient counterforce in the establishment of the "back-check" condition regardless generally of the temperature of the environment in which the door closer operates.
In the typical door closer described above, it is desired that any air or gases entrapped within the fluid and located within the tube portion of the main chamber will be "worked" into the reservoir as the fluid is moved through the passageways to the reservoir. Since air is an easily compressible medium, in comparison to a fluid such as oil, too much air in the main chamber will permit continued, relatively free movement of the door past the sixty to seventy-five degrees opening and lessen the desired effect of the "back check" condition. Therefore, it is desirable to move the air from the main chamber and into the reservoir as the piston is moved upon opening of the door as quickly as possible. However, the portion of the fluid which contains the entrapped air must have an essentially unobstructed path through the main chamber to the reservoir.
Typically, the reservoir is located at the side and extends from the top to the bottom of the cylinder and the air entrapped within the fluid will "work" its way to the upper portions of the fluid at the top of the chamber. As the piston is moved as noted above, the fluid is moved from the main chamber, through the passageways and into the reservoir. However, significant portions of the entrapped air will rise to the top of the tube portion of the chamber and will be further captured between the upper portions of the convolutions of the coil spring within the spring tube. As the fluid is moved through the passageways, the portions of the fluid between the upper portions of the convolutions of the spring will not move and the air entrapped therein also will not move. Thus, some of the more easily compressible air remains in the main chamber and deleteriously affects the operation of the door closer as noted above.
Thus, there is a need for a door closer which will avoid the entrapment of air within the fluid at the top of the main chamber and will allow the air to move desirably from the main chamber into the reservoir.